RU2488786C1 - Manufacturing method of mechanical action sensor, and mechanical action sensor - Google Patents

Abstract

FIELD: measurement equipment.

SUBSTANCE: device includes a sensor base, the maximum thickness of which is much less than two other measurements, a sensing element of elongated shape, which encloses the base with spiral coils so that a short section of each of spiral coils passes throughout the thickness of the base. Short sections of spiral coils are intended for orientation in the plane almost perpendicular to direction of interference effect, and long sections of spiral coils are intended for orientation in the plane almost perpendicular to direction of measured effect.

EFFECT: improving interference resistance of the sensor at performance of measurements.

18 cl, 4 dwg

Description

FIELD OF THE INVENTION

The present invention relates to measuring equipment, and more particularly, to a mechanical impact sensor, intended, for example, for weighing in motion (WIM - Weigh In Motion) of vehicles, and also to a method for manufacturing such a sensor.

State of the art

Currently, there are many different weight sensors used for weighing in the movement of vehicles. These sensors typically use piezoelectric or fiber optic sensors.

For example, Japanese Patent Application Laid-open No. 2009-264748 (publ. 12.11.2009), No. 2010-032358 (publ. 02/12/2010) and No. 2010-185729 (publ. 08.26.2010) disclose pressure-sensitive sensors based on fiber optic cable.

German patent applications laid out No. 102004036729 (publ. March 23, 2006) and No. 102008018671 (publ. 10/15/2009), as well as EPO patent application No. 0384874 (publ. 02/06/1990) describe capacitive piezoelectric sensors installed in the roadway .

A variety of designs of piezoelectric sensors suitable for use in weighing systems are described, for example, in US patent No. 4794365 (publ. 12/27/1988) and No. 5477217 (publ. 12/19/1995), in the application for US patent No. 2009/0021117 (publ. 01/22/2009), in the application for a patent of Great Britain No. 2042256 (publ. 09/17/1980), in the laid out patent applications of Japan No. 10-090086 (publ. 04/10/1998), No. 2007-017421 (publ. January 25, 2007) and No. 2010-071840 (publ. 02.04.2010), in the patent application of Turkey No. 9801893 (publ. 21.04.2000).

All the sensors mentioned above have the disadvantage that their readings (when using such sensors in the roadway) are significantly affected by the interference effect in the form of a surface wave propagating horizontally in the roadway from each passing wheel. As a result, the accuracy of measurements using such sensors is low.

Many different means are known to combat such interference. For example, piezoelectric or fiber optic sensors are placed in a hollow tube, as in the publication of international application No. WO 03/84874 (publ. 06.02.1990). The placement of the piezoelectric sensors in the tube is also described in US patent No. 5206642 (publ. 04/27/1993) and No. 5265481 (publ. 30.11.1993), in Japanese patent application laid out No. 2010-197086 (publ. 09/09/2010). The use of additional gaskets to isolate piezoelectric sensors laid in the roadway from the effects of a surface wave is disclosed, for example, in US Pat. Nos. 5,571,961 (publ. November 5, 1996) and No. 5,666,540 (publ. September 16, 1997), in Japanese Patent Application Laid-Open No. 2002- 063685 (published on February 28, 2002) and No. 2007-240541 (published on September 20, 2007). The most detailed disclosed such means of combating interfering effects in US patent No. 5461924 (publ. 10/31/1995). However, these tools are often not enough to reliably isolate the pressure sensor from the action of a surface wave propagating in the roadway or other medium almost perpendicular to the measured effect. In addition, such additional means for isolating the surface wave greatly increase the cost of the resulting sensors.

In patent application EPO No. 0186534 (publ. 12.11.1985), an attempt was made to circumvent this problem by sectioning the sensor along its length across the roadway. In this case, the signal from the interfering effect (surface wave) is not integrated over the entire length of the sensor (several meters), but only in separate sections (tens of centimeters), which account for the pressure from the wheels of a passing vehicle. In this case, the overall signal-to-noise ratio of such a sensor increases, since the sections that do not produce a useful signal (which do not appear under the wheels of the vehicle) do not participate in the formation of the measurement signal. However, in this case, too, the problem of eliminating the interfering effect, although in a reduced form, remains.

Disclosure of invention

Thus, there is a need for a sensor of mechanical impact (in particular, pressure), which would allow, when installed, for example, in the roadway, to increase the signal-to-noise ratio without large additional costs.

To solve this problem and achieve the indicated technical result, in a first aspect of the present invention, there is provided a mechanical impact sensor for detecting a measurable mechanical effect in the presence of an interfering mechanical effect and comprising: a sensor base, the maximum thickness of which is much less than its other two measurements; an elongated sensitive element covering the base with spiral turns so that a short portion of each of the spiral turns passes through the thickness of the base; while short sections of spiral turns are intended for orientation in a plane almost perpendicular to the direction of arrival of the interfering effect, and long sections of spiral turns are intended for orientation in a plane practically perpendicular to the direction of arrival of the measured effect.

A feature of the sensor of the present invention is that short sections of spiral turns can be coated with a layer of material that reduces the penetration of interfering mechanical stress.

Another feature of the sensor of the present invention is that the sensing element can be made in the form of a piezoelectric cable or fiber optic cable, and the base can be in the form of a rectangular strip on which long sections of spiral turns are located almost perpendicular to the largest dimension of this rectangular strip. In this case, the base may have a cross section in the form of a rectangle or ellipse.

Another feature of the sensor of the present invention is that the sensing element can be made in the form of a strain gauge wire, and the base can be in the form of a rectangular strip, in which the edges of the long sides are bent to the same side, and the long sections of the spiral turns are almost perpendicular the largest dimension of a rectangular strip. In this case, the strain gauge wire can be fixed in contact with the curved edges of the long sides.

Another feature of the sensor of the present invention is that the bending radius between the short and long sections of each of the spiral turns can be selected as minimal as possible from the condition of ensuring the mechanical integrity of the sensing element.

Another feature of the sensor of the present invention is that the spiral coils of the sensing element can be made in the form of separate adjacent sections, the conclusions of each of which are isolated from the measured and interfering influences.

Finally, another feature of the sensor of the present invention is that the sections of spiral turns have a length along the largest dimension of the base is not less than the width of the wheel of the vehicle.

To solve the same problem and achieve the same technical result, in a second aspect of the present invention, there is provided a method for manufacturing a mechanical impact sensor designed to find a measurable effect in the presence of an interfering effect and containing an elongated sensitive element, namely: providing a sensor base, maximum whose thickness is much less than its other two dimensions; cover the base with a sensing element in the form of spiral turns so that a short part of each of the spiral turns passes through the thickness of the base; while the short parts of the spiral turns are intended for orientation in a plane almost perpendicular to the direction of arrival of the interfering effect, and the long parts of the spiral turns are intended for orientation in a plane practically perpendicular to the direction of arrival of the measured effect.

A feature of the method of the present invention is that short sections of spiral turns can be coated with a layer of material that reduces the penetration of said interfering mechanical stress.

Another feature of the method of the present invention is that the sensing element can be made in the form of a piezoelectric cable or fiber optic cable, and the shape of the base can be selected in the form of a rectangular strip and long sections of spiral turns can be arranged almost perpendicular to the largest dimension of this rectangular strip. In this case, the base has a cross section in the form of a rectangle or ellipse.

Another feature of the method of the present invention is that the sensing element can be made in the form of a strain gauge wire, and the base can be in the form of a rectangular strip, in which the edges of the long sides are bent to the same side, and can have long sections of spiral turns almost perpendicular the largest dimension of the strip. In this case, the strain gauge wire can be fixed in contact with the curved edges of the long sides.

Another feature of the method of the present invention is that the bending radius between the short and long sections of each of the spiral turns can be selected as minimally possible from the condition of ensuring the mechanical integrity of the sensing element.

Another feature of the method of the present invention is that the spiral coils of the sensing element can be made in separate sections, the conclusions of each of which are isolated from the measured and interfering influences.

Finally, another feature of the method according to the present invention is that in the case of a sensor intended for weighing the vehicle by weight, the sections of spiral turns can be located on the base at a distance from one another no more than the distance between the inner sides of the wheels of the vehicle that has a minimum spacing wheels on one axle.

Brief Description of the Drawings

The present invention is illustrated by the attached drawings, in which the same elements in different drawings are assigned the same reference position.

Figure 1 shows a conditional view explaining the placement of a sensor for measuring the weight of a passing vehicle in a roadway and the direction of mechanical forces acting on such a sensor.

2 shows one embodiment of a sensor of the present invention.

Figure 3 illustrates an example implementation of the partitioned sensor of the present invention.

4 shows another exemplary embodiment of the sensor of the present invention.

Detailed Description of Embodiments

The mechanical impact sensor of the present invention is intended to detect a measurable mechanical effect in the presence of an interfering mechanical effect. Such a sensor can be used when it is necessary to measure the first force in the presence of a second force directed at an angle to the first.

For example, such a task arises when measuring the weight of a motor vehicle traveling through a sensor 1 built into the surface of the roadway 2 (FIG. 1). At the same time, a mechanical vibration occurs in the roadway 2 propagating along its surface, so that both the weight P of the passing vehicle is simultaneously affected by the sensor 1 (Fig. 1 shows the wheel of this vehicle with a dashed line) and the force K from the aforementioned fluctuations. The weight P is directed vertically at the sensor 1, while the impact K of mechanical vibration in the roadway 2 is directed horizontally.

In the case when the sensor element 1 of the present invention is made in the form of a piezoelectric cable or fiber optic cable that changes its properties when pressed on it, the sensor 1 contains (Figure 2) a base 3, which is usually an elongated plate of suitable material, for example plastic or aluminum. The cross section of this plate may be rectangular or elliptical. It is characteristic that the maximum thickness of such a plate is much less than two other measurements. In Fig.2, the base 3 is shown in the form of a rectangular cross-sectional plate, the thickness b of which is much (at least 5 times) shorter than the width l and length a .

As already noted, in the weight sensors used for weighing in the movement of vehicles, piezoelectric or fiber optic sensors are most often used. It is also possible to use such sensing elements in the sensor of the present invention. In figure 2, the sensing element 4, which is a long piezoelectric or fiber optic cable, covers the base 3 with spiral turns. In figure 2, these spiral coils are shown spaced apart from each other in increments of h, however this is not necessary, and the coils can be located close to each other. The long section of each of these spiral turns extends along the width l of the base 3, and the short section of each of the spiral turns extends along the thickness b of the base 3. Thus, the sensor 1 is obtained in the form of a long spiral wound on the base 3.

Sensor 1, if it is intended to be installed in the roadway 2, should be placed across the direction of movement of vehicles traveling along this roadway 2. Moreover, short sections of spiral turns are intended for orientation in a plane almost perpendicular to the direction of arrival of the disturbing effect (in this case , efforts K in Fig. 1), and long sections of spiral turns are intended for orientation in a plane almost perpendicular to the direction of arrival of the measured impact (in annom case, force F in Figure 1). Any of these effects is perceived by the sensitive element 4, if any of its segments is located at some angle to the direction of arrival of this effect. Or - what is the same - the intensity of the signal that occurs in the sensitive element 4 under the influence of a certain influence is proportional to the projection of the corresponding segment of the sensitive element 4 on a plane perpendicular to the direction of arrival of this effect.

The spiral turns of the sensor element 4 on the base 3 can be wound in different ways. For example, if the long sections of the spiral turns are perpendicular to the length a of the base 3, then the short sections of these spiral turns will pass through the thickness b at a certain angle. In this case, the measured effect (i.e., weight P) will be perceived by all - both long and short - segments of spiral turns. Since, as indicated above, b << l, we can approximately assume that the measured effect will be perceived by the entire spiral turn, i.e. its entire length equal to 2 (l + h). The interfering effect (i.e., the force K) will be perceived only by short segments of spiral turns, since long segments are turned by their ends to the direction of arrival of this force K. Therefore, the perception of the interfering effect K will be carried out on each spiral coil for a length of 2h. Then the ratio of the signals from the measured and interfering effects in the sensing element 4 will be approximately proportional to (l + h) / h.

.Spiral turns can be wound in another way. For example, they can pass obliquely in width l and perpendicularly in thickness 6 (oblique winding). Then it is easy to show that the ratio of the signals from the measured and interfering effects in the sensing element 4 will be approximately proportional $$\sqrt{l^2+h^2}/h$$

.

.In the case of sawtooth winding, when the short sections extend perpendicularly along the thickness b, the long section on the upper side of the base 3 runs obliquely along the width l, and the long section on the lower side extends perpendicular to the width l, it can be shown that the ratio of signals from the measured and interfering influences in the sensing element 4 will be approximately proportional $$(l+\sqrt{l^2+\mathrm{four}{h}^2})/2h$$

.

As can be seen from these expressions, it is preferable to wind the spiral turns of the sensitive element 4 on the base 3 so that their long sections are perpendicular to the direction of arrival of the interfering effect. For the case of a sensor designed to measure the weight of a passing vehicle, it is advisable to arrange long sections of spiral turns of the sensing element 4 perpendicular to the largest size of the base 3 (i.e., length o in FIG. 2). With this arrangement of spiral coils, it is preferable to cover their short segments with a layer of material that reduces the penetration of interfering mechanical stress. In particular, as shown in FIG. 2, it is possible to place on top of the entire narrow side of the base 3 (thickness 6), along which short segments of spiral turns of the sensing element 4 pass, a layer that absorbs (reflects) the elastic vibrations propagating in the road surface 2. As such a material, any suitable material may be selected, for example rubber or polystyrene foam (see also the aforementioned Japanese Application No. 2010-071840 and US Patent No. 5461924).

When winding spiral coils of the sensing element 4 onto the base 3, the mechanical strength of the material of which the winding cable is made should be taken into account. In particular, the bending radius between the short and long sections of each of the spiral turns should be chosen as minimal as possible from the condition of ensuring the mechanical integrity of the sensing element 4.

However, a strain gauge wire that changes its tensile conductivity can also be used as a sensitive element. In this case, the sensor 1 contains (Figure 4) a base 3, which in this case is made in the form of a rectangular strip, the edges of the long sides of which are bent to the same side (upwards in Figure 4). As in FIG. 2, the maximum thickness b of such a plate (taking into account the bent edges) is much smaller than the other two dimensions ( a and l). As the material of such a strip, any non-conductive material, for example, plastic, can be used.

In Fig. 4, long sections of spiral turns are located almost perpendicular to the largest dimension a of said rectangular strip. Of course, all of the above for Figure 2 about the location of the spiral turns, applies in this case. The strain gauge wire is fixed at the points of contact of the spiral turns with the curved edges of the long sides. The base 3 can also be made in the form of two strips with bent edges connected by their convex parts, so that in the cross section of the base 3 a figure resembling the letter “X” is formed. In this case, short sections of spiral turns will extend in a vertical or inclined direction in FIG. 4. It is also possible here to use a layer of material that absorbs interference on the sides of the base 3.

Although in FIGS. 2 and 4, the sensor 1 is depicted consisting of spiral coils wound one after another by a continuous cable or wire, such an implementation of the sensor 1 is optional. For example, the sensor 1 can be made so that the spiral turns of the sensing element 4 are made in the form of separate adjacent sections, as is the case in the aforementioned EPO application No. 0186534. Such an embodiment is shown in FIG. 3. Moreover, the individual sections 5 of which the sensing element 4 consists have a length along the largest dimension of the base 3 (i.e., along the length a ) of at least the width of the wheel of the vehicle. Of course, the wheel having the largest width should be selected as such a wheel. The conclusions 6 of each of the individual sections 5 are isolated from the measured and interfering effects, for example, by placing them inside the tube from the material noted above, absorbing (reflecting) the elastic vibrations propagating in the road surface 2. As an alternative, it can be proposed to be placed at the ends of the cable , from which each individual section 5 is wound, corresponding converters, providing the conversion of the signal generated in the section into an electrical signal. For example, when using the optical fiber sensing element 4, these will be photoelectric or photoelectric converters known to those skilled in the art.

The operation of the proposed sensor is as follows.

After placing the sensor 1, made in the above way, in the road surface 2 flush with the surface of this surface or under a protective film, to extend the life of this sensor 1, the terminals 6 of the sensor 1 or each section 5 thereof are connected to the corresponding meters. In particular, if the sensor 1 is made on a piezoelectric cable or strain gauge wire, the conclusions 6 of each section can be connected to the measuring bridge; if the sensor 1 is made on a fiber optic cable, the conclusions 6 of each section are first converted into electrical signals, which can then be processed in analog or digital form, as is known to specialists.

When the wheel of a vehicle is hit by a sensor 1 located in the road surface 2, the force P acts on the sensor 4 of the sensor 1, causing a change in the physical properties of the sensor. If the sensing element 4 is made in the form of a piezoelectric or fiber optic cable, the action of the force P compressing the cross section of this cable will cause a change in the transmittance of the electric or light signal through the cable. If the sensing element 4 is made in the form of a strain gauge wire, the action of the force P spreading to the sides of the edge of the base 3 (see Figure 4) will cause the strain gauge wire to stretch and, as a result, increase its resistance. These changes are measured by appropriate meters. However, the sensor 1 is also affected by the interfering effect K, which distorts the measurement. The proposed design of the sensor 1 due to the specific location of the sensing element 4 allows to reduce the influence of interfering effects and thereby increase the signal-to-noise ratio at the output of such a sensor, which leads to an increase in measurement accuracy.

Thanks to the described sensor manufactured in the manner described above, it is possible to sharply reduce the cost of not only the manufacturing process, but also the installation process of such sensors, since the sensor can be completely manufactured in an industrial environment, and when it is installed in the roadway, complex canalization operations are not required for sensor, as is the case in the analogues described above.

Claims (18)

1. The mechanical impact sensor, designed to find the measured mechanical stress in the presence of interfering mechanical stress and containing:
- the base of the sensor, the maximum thickness of which is much less than its other two measurements;
- an elongated sensing element covering said base with spiral turns so that a short portion of each of said spiral turns passes through the thickness of said base;
- while the above-mentioned short sections of spiral turns are intended for orientation in a plane almost perpendicular to the direction of arrival of the said interfering effect, and the long sections of these spiral turns are intended for orientation in a plane practically perpendicular to the direction of arrival of the said measured influence. 2. The sensor according to claim 1, in which the aforementioned short sections of the spiral turns are covered with a layer of material that reduces the penetration of said interfering mechanical stress. 3. The sensor according to claim 1, wherein said sensing element is made in the form of a piezoelectric cable or fiber optic cable, and said base is made in the form of a rectangular strip on which long sections of said spiral turns are located almost perpendicular to the largest dimension of said rectangular strip. 4. The sensor according to claim 3, in which said base has a cross section in the form of a rectangle or ellipse. 5. The sensor according to claim 1, in which said sensing element is made in the form of a strain gauge wire, and said base is made in the form of a rectangular strip, in which the edges of the long sides are bent to the same side, and said long sections of spiral turns are located almost perpendicular the largest dimension of said rectangular strip. 6. The sensor according to claim 5, in which said strain gauge wire is fixed in contact with said curved edges of the long sides. 7. The sensor according to any one of the preceding paragraphs, in which the bending radius between the aforementioned short and long sections of each of these spiral turns is selected as minimal as possible from the condition of ensuring the mechanical integrity of the said sensing element. 8. The sensor according to claim 1, in which the said spiral coils of the sensing element are made in the form of separate adjacent sections, the conclusions of each of which are isolated from the aforementioned measured and interfering influences. 9. The sensor of claim 8, in which the said sections of the spiral turns have a length along the largest dimension of the said base is not less than the width of the wheel of the vehicle. 10. A method of manufacturing a mechanical impact sensor, designed to find the measured impact in the presence of an interfering effect and containing a sensitive element of elongated shape, namely:
- provide a sensor base, the maximum thickness of which is much less than its other two measurements;
- cover said base with said sensing element in the form of spiral turns so that a short section of each of said spiral turns passes through the thickness of said base;
- while the above-mentioned short sections of spiral turns are intended for orientation in a plane almost perpendicular to the direction of arrival of the said interfering effect, and the long sections of these spiral turns are intended for orientation in a plane practically perpendicular to the direction of arrival of the said measured influence. 11. The method according to claim 10, in which said short sections of spiral turns are coated with a layer of material that reduces the penetration of said interfering mechanical effect. 12. The method according to claim 10, in which said sensing element is made in the form of a piezoelectric cable or optical fiber cable, and the shape of said base is selected in the form of a rectangular strip and said long sections of spiral turns are arranged almost perpendicular to the largest dimension of said rectangular strip. 13. The method of claim 12, wherein said base has a cross section in the form of a rectangle or ellipse. 14. The method according to claim 10, in which said sensing element is made in the form of a strain gauge wire, and said base is made in the form of a rectangular strip, in which the edges of the long sides are bent to the same side, and said long sections of spiral turns are arranged almost perpendicularly the largest dimension of said rectangular strip. 15. The method according to 14, in which said strain gauge wire is fixed in contact with said curved edges of the long sides. 16. The method according to any one of claims 10 to 15, in which a bend radius between said short and long sections of each of said spiral turns is selected as minimally possible as possible to ensure the mechanical integrity of said sensor element. 17. The method according to claim 10, in which said spiral coils are made of separate sections, the conclusions of each of which are isolated from said measured and interfering influences. 18. The method according to 17, in which the said sections of the spiral turns have a length along the largest dimension of the said base is not less than the width of the wheel of the vehicle.

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